Thank-you for the great tutorial. I've been experimenting with a few HDR images and am unsure whether the results are good or not. I'm colour blind with quite a few shades of colour and thus am never sure whether images look good or not.

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Well, color-blind Now I assume you have to decide between processing the images in a way that you are satisfied or that other people are. Is that so?

As to your Q relating to dark and/or overcast light. If you mean light that produces dull colors then you're right: HDR can map brightness values to colors in a way that the results looks more colorful than the unprocessed image. But it need not be so. There are many ways to tone-map and some people try to avoid the overly colorful look. So it depends.

If you look at shoots that are taken in very low light these mostly have very high contrast as some parts of the image lie in total shadow whereas some other parts are probably shone on by some street light or other light-source. In those cases HDRing the image can compress the extreme dynamic range of the original and produce an image where you can discere details in the darkest shadows and details under the light. But this does not necessarily mean you get some "boosted" colors.

ive just tried this, looking at a landscape into the sun whilst its setting, did 5 exposures, +4 +2 0 -2 -4 but for some reason the sky looks fine the but the ground its pure black and dark, what did i do wrong?

Yes you can if you want, it takes extra time so make sure there is not much movement in the frame, but just put the camera in aperture priority and change the shutter speed (by exposure compensation) to 1 stop lower and after 1 stop higher than the optimal exposure. Or +2 and -2, and even +2, +1, 0, -1, -2 is possible.